October 2017Acoustic Energy AE1 Active MonitorMartin Colloms assesses the new active version of a classic miniature loudspeaker.
Review By Martin Colloms

AnAE1 was the
first ever Acoustic Energy loudspeaker. It was designed by Phil Jones back in
1987, as a high power desktop (meterbridge) miniature monitor which could play
rock music much louder than its similarly sized, contemporary LS3/5a.
The '3/5a came real wood veneered; the AE1
was finished in durable Pro-style black textured paint.

The AE1 also had
pure piston technology that was advanced for the time, with a hard-anodised
aluminium alloy bass/mid driver in a chassis of just 11cm, and a 25mm aluminium
dome for the high frequencies. Internal cables were Teflon insulated Litz and
the enclosure was heavily damped and reinforced with a cast mineral lining. And
it could take high power – about double that of its nearest rivals.

The AE1 was
unashamedly a nearfield monitor, and underwent some mild adjustments in 1980
better to balance it for use in free space when marketed for domestic hi fi. It
was famously and most frequently mounted on those characteristic (and first
rate) heavy duty stands of cast and fluted extruded aluminium alloy (of which I
still have a pair). The loudspeaker has evolved though many iterations over the
past 30 years, with several 'reference' versions and a number of lower cost
spin-offs. While the passive version continues, Acoustic Energy has now directed
its attention towards a well-priced active version of the domestic AE1.

Current MD and R&D chief Mat Spandl was electroacoustic
design engineer at Acoustic Energy for some years before gaining further Pro
audio experience at the Martin Audio division of Harman Professional. Returning
to Acoustic Energy, he was part of the buyout plan that has returned the company
to UK management and ownership (after a long and successful financial
partnership with Formosa Pro-Sonic). He understands the important contribution
full active technology could make to an inexpensive loudspeaker design and has
applied it to this thorough reworking of the AE1
concept.

It costs just £1000/pr for the standard finish, including
four on board power amps. While piano lacquer is standard for black and white,
cherry veneer adds another £200. The new Reference
stands cost another £200 when bought with the speakers (£350 if
purchased separately). The stands are good quality, made of high density
material with a matching veneer inlay, and come with vibration controlling pads
to the loudspeaker underside, plus a set of adjustable floor spikes, or footers
for non-carpeted floors. The stands make a good fit, mechanically, visually and
acoustically.

(Incidentally, Phil Jones himself, now based in the US, has
brought out a near equivalent two-way compact active at a similar price. His
Airpulse Model-1 is differentiated by a 75mm ribbon tweeter, together
with both analogue and wireless streaming connectivity; it is powered from
switch-mode power supplies. Also in contention is the active KEF LS50
Wireless, another compact two-way with a 5in bass/ mid driver, and
comprehensively App controlled. It's priced at £2,000/pr which includes some
advanced features such as UniQ concentric driver technology, deep acoustic
adjustability, and even programmed phase compensation.

The AE1 Active has
no remote handset, no digital input, no WiFi control and no App connectivity; it
is simply connected via the XLR
balanced, or RCA phono socket unbalanced inputs. Appropriately lengthy
interconnect cables to a volume controlled music source, pre-amp, streamer-DAC
or DAC will be needed. Pre-set volume controls on the back help achieve optimum
sensitivity, and subtle switched settings (-2dB, 0, +2dB), for bass and treble
tweak these loudspeakers to the room acoustics, taste and system. The input
impedance is quite low, so do check that the source is happy with such a
loading.Valve pre-amp use is presently contraindicated by that low 2.5kohm value for the RCA input sockets, but we understand that this is being altered to a more satisfactory 10kohm on future production.

This speaker will play louder than the old AE1
as it has a larger 13cm bass compared with the 11cm of its
predecessor. (A sound output of 115dB/m short term is claimed.) As is common
these days, the tweeter has a small waveguide for a smoother off-axis response
(see pic for AE1 Active waveguide
performance at 3.6kHz).

The enclosure is substantially built from cross-braced 18mm
MDF panels, internal damping laminates suppressing any structural resonances.
Two 50 Watt Class A/B linear amplifiers per loudspeaker are directly coupled to each
driver. The physics of active design tells us that such a system will feel more
like 200W/ch of normal stereo drive – and it does! A horizontal reflex port
slot with rounded edges is located on the back panel, above the full area alloy
plate heat-sink and control panel. Standard IEC mains sockets are provided with
modest 1.5m cables, and the supplied RCA/phono interconnects are 3m.

Sound QualityI left them running for a few days, partly for me to
acclimatise to these little compacts after prolonged experience with my own
Magico S5IIs, which are some 50
times the cost of the AE1 Active (and
that doesn't include the Naim power amp). We also used the loan Linn Klimax
Katalyst streamer (review next issue), with its balanced audio
outputs and great App-controlled remote volume facility.

Using studio grade balanced cables to the speakers, the AE1
Actives drove the music with great clarity and detail, and possessed
transparency that was well beyond their price class. With the Naim NDSstreamer-DAC
and the Townshend Allegri control
(the latter well suited to driving lower impedances and the longer cables
required), first impressions were of fine stereo depth, detail and imaging, but
also some excess richness and loss of timing in the bass and lower mid. I did
initially try stuffing the ports, to good overall effect but at a cost of
reduced lower bass and slightly softened dynamics. The designer suggested a -2dB
setting on the bass control, and in my room this result was like the story of
Goldilocks, the three bears, and the porridge that was just right!

With some judicious adjustment of location (iefree
space, out into the room, facing almost straight ahead, grilles off, and it
still looks good, and the tiny indicator lights are not too bright), a variety
of familiar tracks were despatched with aplomb. The soundstage was deep and
wide, it focused stably across the stage and in the depth planes, while solo
piano, orchestral, rock pop and jazz all fared rather better than you could have
any right to expect. I had no problem living with them over the review period,
admiring the high level of musical detail retrieved, and not least the low
levels of listening fatigue.

Among many tracks, I drove it unmercifully with Solti's Mahler
2 (Decca), Fink's See It All,
and also those often troublesome multiple marimbas on Reich's Mallet
Instruments. It caressed the potentially strident soprano sax of Jan
Garbarek, while Lana Del Rey crooned engagingly. Adjusted for '-2' in the
bass, the low frequency timing was well above average, and my rock tracks were
foot tappingly good. It was so easy to forget the size and price and imagine one
was listening to a model at twice the size and cost, so great is the performance
improvement available from a full active design.

ConclusionsI kept thinking of minor criticisms and balancing comments
which would be more appropriate for a £2,000/pr model rather than a loudspeaker
that costs around £1,000, and also includes power amplification. Although this
compact design is in the small monitor class, it punches well beyond its size
and price. Technically it is respectably accurate and the two channels are well
matched. It has low coloration, with very fine driver output integration.
(It's effectively impossible to tell where one leaves off and the other
begins.) For the size and price it also demonstrated a fine dynamic range
together with a very well controlled and informative bass. It is capable,
musical, entertaining and clearly great value. Noting the imminent change to a
higher line input impedance, regardless of whether a specific system might
benefit, a Best Buy rating is clearly appropriate.

Test ResultsDistortion results at 90dB (1m, 50Hz) were good for the size,
with 0.6% second and about 2% third harmonic. By 500Hz the results were a very
good 0.25% second and 0.13% third, with fourth harmonic at an even lower 0.033%
(-70dB). At 1kHz we measured a reasonable 0.3% second and a good 0.15% third,
and at 2kHz there was a mild decline to 0.32% second and 0.35% third. However,
high frequencies were fine by 5kHz, with just 0.08% second and 0.05% third.
Taken overall, these are good results for the size and price.

The on-axis frequency response was a respectably uniform
+/-2.5dB (100Hz to 20kHz), noting a mild dip at 19kHz. Beyond this is found the
usual dome resonance, deferred to 25kHz and of moderate Q (a likely inaudible
+6dB). Mild excess is visible at 1.5kHz, but it's only moderately audible at
+1.5dB, while the bass (at the preferred -2dB setting) extends to 43Hz -6dB
– good for the size, and well-tuned. The off-axis output is clearly well
integrated, both below and above the axis, while the important 30 degrees
lateral response is particularly neutral. The sidewall reflections will
therefore sound quite neutral; only by 60 degrees lateral was a dip more
noticeable, and even then this was comparatively mild.

The in-room output of the pair (averaged 64 times over
listener positions and channels) was substantially flat from 80Hz to 4kHz, which
is quite an achievement, and shows a smooth diminution beyond these limits. The
waterfall decay response shows good phase integration for the early responses,
with a rapid decay thereafter. Some minor clutter is seen later on, but this
remains a good result at the price.